Functional Safety 2016

SIF too slow

• Instrumentation solutions to speed up the SIS response time

• Allow the SIS Response time to be >50% of Process Safety Time

(ref [6] states

“Given the degree of uncertainty in the process safety time, the SIS should be capable of completing

its action within one-half of its allocated process safety time”)

• Go back to SIL assessment… is the hazard really credible?

Process Safety Time

SIS Response Time

Ref [6] ISA-TR84.00.004 part 1